Phonographic apparatus



April 1942- w H. J. HASBROUCK, JR 2,280,763

PHONOGRAPHIC APPARATUS Filed March 30, 1940 Patented Apr. 21, 1942PHONOGRAPHIC APPARATUS Harold J. Hasbrouck, Jn, Merchantville, N. J.,assignor to Radio Corporation of America, a

corporation of Delaware Application March so, 1940, Serial No. 326,896

6 Claims.

This invention relates to phonographic apparatus, and more particularlyto a signal transand the noises radiated either directly by the pick-updevice and/or the records themselves in reacting on the needle. Variousattempts have been made to reduce these extraneous noises,

such as using lighter needles or designing the pick-up for lowereffective mass, but these and other similar attempts have not solved theproblem satisfactorily.

The primary object of my present invention is to provide an improvedpick-up device which will be free from the aforementioned defects.

More particularly, it is an object of my present invention to provide animproved pick-up or sound translating device which will not cause therecord with which it is cooperating during reproduction to radiateextraneous sounds and which will not in itself produce such sounds.

Another object of my present invention is to provide an improved soundtranslating device as aforesaid which will operate with a very lightneedle pressure upon the record, thereby assuring longer record life.

Still another object of my present invention is to provide an improvedsignal translating device wherein the operating parts are light inweight and have minimum inertia effects during operation.

A further object of my present invention is to provide a signaltranslating device for phonographs which is particularly adapted for usewith records of the lateral cut type.

Still a further object of my present invention is to provide an improvedpiezo-electric generator for the reproduction of sound from phonographrecords wherein the operative parts of the generator are well protectedagainst injury.

Another object of my invention is to provide an improved phonographneedle for use in sound reproducing devices of the electro-mechanicaltype.

It is also an object of my present invention to provide an improvedsound translating device of the type set forth which is very simple inconstruction and highly emcient in use.

In accordance with my invention, I preferably employ a piezo-electricunit of the multiple-plate flexing type, the plates or crystals beingdisposed in a horizontal position. To one end of the unit is attached arigid torsion member which is adapted to oscillate slightly and therebyset up torsional strains in the piezo-electric unit which converts theminto corresponding electromotive forces. The free end of the torsion armmay be provided with the conventional needle socket in which my improvedneedle may be removably secured. The needle comprises a rigid arm whichextends downwardly to within about of an inch of the record and in thelowerend of which is swaged or otherwise suitably secured a wire oftungsten or other suitable wear resistant material having a diameter ofapproximately 0.006 inch to 0.010 inch. The wire is substantially L-shaped and extends from the aforementioned arm about inch, beingflexible both vertically and horizontally, or, in other words, in planesboth normal to and parallel with the record. The free end of thetungsten wire is bent downwardly for about 7 of an inch to provide therecord groove engaging tip. Practically all motion is confined to thispiece of wire, the arm itself, the torsion yoke, and the piezo-electricunit moving very little. A suitable guard protects the wire from injuryand a rubber bumper located adjacent the bend in the wire helps takeshocks such as that resulting from accidental dropping of the pick-up onthe record. An additional guard is provided behind the record engagingtip of the needle to prevent the tip from being accidentally bentbackward. My improved pick-up preferably operates with a verticalpressure of about one-half ounce to one ounce and is good for at least2000 playings on shellac records by reason of the wear resistant qualityof the tungsten wire. Since the wire needle is arranged to have amaximum of vertical flexibility, it is obvious that it will impart onlyvery small forces to the record and thus reduce the generation of thewave motion in the record and subsequent radiation of the noiseordinarily created by such radiation. Furthermore, since the diameter ofthe wire needle remains constant throughout its life, it is obvious thatthe needle groove will not be subjected to undue wear.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood from the following description of one embodiment thereof whenread in connection with the accompanying drawing in which Figureil is atop plan view of a sound translating device constructed accordingto mypresent invention and mounted on a suitable nick-up arm,

Figure 2 is an enlarged plan view of the pickup device itself,

Figure 3 is a sectional view taken on the line III-III of Fig. 2,

Figure 4 is a fragmentary sectional view showing the position of theneedle in relation to associated parts when the needle tip is inengagement with a record, and

Figure 5 is a fragmentary detail view looking in the direction of thearrow A of Fig. 3.

Referring more particularly to the drawing, wherein similar referencenumerals indicate corresponding parts throughout, I have shown a casingmember lformed in two parts and preferably hermetically sealed toenclose a piezo-electric unit comprising a pair of piezo-electriccrystals 3 of Rochelle salt or the like, with which are associatedterminal foils 5 of conductive material in well known manner, thecrystal unit 3 being spaced from the casing l by suitable blocks I ofdamping material such as that known commercially as DuPont Viscaloid No.'7. The casing I also carries a torsion yoke 9 within a rubber sleeveII, the outer or free end of the torsion yoke 9 being provided with aneedle socket l3, and the inner end of the member 9 being provided witha yoke or clamp I5 which firmly clamps one end of the crystal .unit 3.The device thus far described is more or less conventional and may bemounted upon a suitable pickup arm I! which is pivotally mounted on asuitable support (not shown) for movement over a phonograph record inwell known manner.

Removably received within the socket i3 and clamped to the torsionmember 9, as by a set screw I9, is a rigid arm or rod 2| which extendsdownwardly substantially at right angles to the plane of the crystalunit 3. Suitably secured to the lower end of the rod 2|, as by swagingor the like, is a forwardly extending thin, flexible, L- shaped needle23of music wire or the like and preferably formed of tungsten or someother wear resistant material or alloy of metals. The

major portion of the needle 23 extends substan- When the pick-up deviceis in cooperative-relation to a record, the crystal unit 3 occupies asubstantially horizontal position. Th needle 23 is flexible in alldirections (that is, through 360) in a plane at right angles to themajor portion, or the horizontal arm, of the needle but it is fairlyrigid in torsion. Consequently, the needle tip 25 can faithfully followthe contours of a lateral cut groove and impart a twisting action ortorsion to the torsion member 9 through the connecting arm 2 I, theneedle itself movin arcuately as a whole about the axis of the yoke 9 asa center without itself undergoing any substantial twisting action sinceit is rigid in torsion. This, in turn, sets up torsional strains in thepiezoelectric unit 3 to generate electromotive forces corresponding tothe mechanical impulses derived by the needle tip 25 from the record,and the resulting electromotive forces may be transferred to suitableamplifying apparatus and a loudspeaker through the leads 5. Since theneedle 23 is flexible in both a plane normal to the record and a planeparallel with the record, it is obvious that the needle 23 will impartonly very slight forces to the record, thereby reducing the generationof the wave motion by the record. Hence, the subsequent radiation ofnoises such as are characteristic of the prior art phonographs will bealmost entirely eliminated.

The improved pick-up device heretofore described is very compact andlight in weight and has a needle pressure of from about one-half ounceto one ounce. Because of the flexibilitymf the needle 23, it isadvisable to provide additional support for the pick-up device. For thispurpose a guard 21 may be secured to the bottom of the casing l. Theguard 21 extends forwardly over the needle 23 and is provided with anopening 29 through which the connecting arm 2| extends. At its forwardend, the guard is bent downwardly and is bifurcated, as clearly shown inFig. 5, so

that it is adapted to straddle the needle 23 at substantially the bendtherein. Secured to the guard 21 above its bifurcated portion is a plate3| to the underside of which is secured a rubber block 33 which. acts asa bumper for taking up the shock which the pick-up may receive whenaccidentally dropped onto the record. The bifurcated downwardlyextending end of the guard 21 has fixed thereto a secondary or auxiliaryguard in the form of a wire 35 which is mounted slighlty behind theneedle tip 25 and beneath the major portion of the needle 23, the guardwire 35 preventing the needle tip 25 from being accidentally bent backout of place, since the needle tip 25 projects down below the bifurcatedextension of the guard 21 only a very short distance. Duringreproduction, as the needle tip 25 rests on the record, the needle isspaced slightly vfrom the guard 35 and engages the rubber bumper 33, asclearly shown in Fig. 5. Thus, the rubber bumper 33 is also adapted toact as a bearing for the needle 23.

Although I have shown and described but one embodiment of my invention,I am fully aware that many other modifications thereof are possible. Forexample, instead of removably mount-' ing the arm 2| in the torsionmember 9, it may be fixed thereto and made a permanent part thereof.Also, it will be obvious to those skilled in the art that my improvedneedle is not necessarily limited to use with a crystal pick-up, but maybe used with a pick-up or generator of the electromagnetic, dynamic,condenser or any other suitable type. Furthermore, if it is desired, thebumper 33 may be made of any other suitable material than rubber, or itmay even be dispensed with entirely. Also, if desired, the major, horizontal portion of the needle 23 may be made of piano wire and thedownwardly extending needle tip 25 may be made of tungsten or otherwearresistant metal and welded, or otherwise suitably operate with aphonograph record, the combination of an oscillatably mounted yokemember having a free end, a rigid arm secured to said yoke memberadjacent the free end thereof, and a thin needle formed of wire securedto said am and extending forwardly thereof, said needle having a bendtherein adjacent its free end to provide an ofiset needle tip adapted totrack the record groove, and said needle being substantially rigidtorsionally whereby it is adapted to oscillate' said yoke member butbeing flexible in planes both parallel with and normal to thecooperating record. 7

2. The invention set forth in claim 1 characterized in that said arm isremovably received by said yoke member.

3. A phonograph needle comprising a member having a relativelyelongated, flexible portion which is substantially rigid torsionally butflexible in all directions in a plane normal thereto, and a relativelyshort portion integral with and extending at an angle to saidfirst-named portion and constituting a record-engaging tip, saidelongated portion being mounted to move arcuately as a whole in-responseto lateral actuation of said tip portion by a record.

4. A phonograph needle for cooperation with a record having a laterallyundulating groove comprising a member having a. relatively elongated.flexible portion which is substantially rigid torsionally but flexiblein all directions in a plane normal thereto, and a relatively shortportion extending from said first-named portion at substantially a rightangle thereto, said short portion constituting a record-engagingtip'adapted to be actuated by the undulations or th groove and totransmit the undulatory movement thereof to said first-named portion tocause said first named portion to move arcuately as a whole incorrespondence with said undulations by reason of the torsional rigidityof said first-named portion.

5. A phonograph needle according to claim 4 characterized in that saidfirst-named portion is constituted by a metallic wire having a diameterof approximately 0.006" to approximately 0.010".

6. A phonograph record according to claim 4 characterized in that saidfirst-named portion has a length of the order or /4" and saidsecondnamed portion has a length or the order of $6 5.

HAROLD J. HASBROUCK, JR.

